This research is concerned with explaining pregnancy risk-taking (having coitus without use of an effective method of birth control) among adolescent females. The research will specify the relative contribution of a theory first developed by Kristin Luker which posits that at each coital event, a cost-benefit set toward contraceptive use and pregnancy is operative. This set coupled with subjective assessments of the probabilities of pregnancy and pregnancy reversal then determine the likelihood that a woman will engage in risk-taking during that event. In order to develop a more comprehensive model, the research will examine the contribution of the Luker model relative to the theoretical contributions of levels of ego development and knowledge about contraception. Because of the crucial importance of access to contraceptives within this age group, testing of these explanations will be carried out with access to contraceptives controlled. Interviews will be conducted with a sample of 600 young women who attend a multi-service center for adolescents in New York. The theoretical importance of this study is its linking of psychological explanations, service-related explanations, and the cost-accounting processes of young people relative to pregnancy risk-taking. The research is of practical significance in that it focuses on a group for whom the negative consequences of pregnancy have now been well documented. The findings should offer needed directions to those who staff programs for young people.